The Digestive System
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The Digestive System
The body needs a constant supply of food as fuel for energy if it is to remain healthy and active.
The digestive system makes food soluble and breaks it down into molecules small enough to pass into the bloodstream and be transported to the muscles and organs.
Digestion starts in the mouth where food is ground up by the teeth to form a pellet of food called a bolus. It is then easily swallowed.
While in the mouth an enzyme released from the salivary gland called ptyalin begins to turn starch into sugar.
Food is pushed down the oesophagus (gullet) by a wave like action called peristalsis.
When reaching the stomach, foods are mixed with gastric juices containing more enzymes and dilute hydrochloric acid.
Food is released into the duodenum in small amounts with the relaxation of the pyloric sphincter. It spends approximately six hours here.
Food is further digested by the action of a large number of alkaline enzymes.They break down food into a mixture of simple amino acids, fatty acids and glycerol.
Undigested waste food passes into the colon (the large intestine) where it remains for twelve hours while more nutrients and water are absorbed into the bloodstream.
The solid remains pass through the last part of the system where they leave the body through the anus.
Waste fluids are taken to the kidneys. Here they are filtered off and pass as urine through the ureters to the bladder..
The urine is expelled from the body through the urethra.
|End product:||Where taken:||Uses:|
|Amino acids.||Taken into the bloodstream to the body tissue.||Build new amino acids. Repair new tissues.|
|Simple sugars.||Taken first into the liver and then to the muscle cells.||Energy.|
|Fatty acids and glycerol.||Carried in the lymph vessels to the venous system.||Energy stores. Heat insulation.|
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